Investigation of patients with Neurological Dysfunction. The general aim of this project is to obtain more precise understanding of multiple factors possibly related either singly or in combination to the pathogenesis of a number of neurological disorders including multiple sclerosis, myasthenia gravis, polyneuropathy and other neuromuscular diseases. The studies of multiple scelrosis include a detailed evaluation of the histocompatibility makeup and the relationship between immunogenetic background and clinical disease as well as immunological function including the cellular response to various human viruses. Magnetic resonance imaging is being used to assess the extent and magnitude of lesions in the white matter. These studies are performed in patients with sporadic disease, patients with a family history of demyelinating disease as well as identical and nonidentical twins who are either concordant or discordant for the disease. Cerebrospinal fluid immunoglobulin content and specificity are being evaluated by new highly sensitive techniques. Trials of experimental therapeutic approaches are being conducted in carefully selected patients with multiple sclerosis. One phase I trial currently in progress involves the administration of Poly ICLC, and interferon inducer. In another phase I trial blood lymphocytes are being transferred from a normal person to an identical twin with multiple sclerosis. A phase III cooperative trial of cyclosporine A in chronic progressive multiple sclerosis has been initiated. Patients in this study are randomized into groups that are treated with either cyclosporine A or placebo.